1. Field of the Invention
The present invention is related to a power adaptor and a power conversion method, and more particularly, to a power adaptor and a power conversion method with a power-saving mechanism.
2. Description of the Prior Art
A power adaptor is configured to convert high-voltage alternative-current (AC) or direct-current (DC) power into low-voltage DC power. Power adaptors are widely used in various electronic devices as power supplies. Common power adaptor structures include flyback, forward and push-pull. Flat-panel devices normally adopt external power adaptor due to limited space.
FIG. 1 is a diagram illustrating a prior art external power adaptor 100 in operation. The power adaptor 100 is configured to convert an input voltage VIN provided by an AC power 12 into an output voltage VOUT for operating a loading device 14. The loading device 14 may be a notebook computer or a liquid crystal display panel which requires a lower operating voltage in a power-saving mode and a higher operating voltage than in a normal mode. The power conversion ratio (VOUT/VIN) of the prior art external power adaptor 100 is determined by the voltage required for operating the loading device 14 in the normal mode, and remains constant whether the loading device 14 functions as a heavy load (normal mode) or a light load (power-saving mode). Therefore, when the loading device 14 enters the power-saving mode, the prior art power adaptor 100 may provide the output voltage VOUT higher than required, thereby causing excessive power consumption.